HELIUM CHRONOMETRY OF APATITE AND TITANITE USING ND-YAG LASER HEATING

Abstract

We developed a technique for extracting 4He from apatite and titanite using laser heating that permits measurement of U and Th and, hence, (U-Th)/He ages, on a single sample aliquot. Unlike direct laser heating, quantitative He extraction and U, Th retention can be achieved when samples are indirectly laser heated to temperatures below their melting point. Resulting He ages are consistent with those obtained from conventional furnace heating of larger samples. The major advantages of this technique include faster analysis and far lower, more reproducible He blanks that permit single crystal analyses. Single crystal dating opens a variety of new avenues for (U-Th)/He chronometry.